Air Gap CV measurement for doping concentration in epitaxial silicon

Epitaxial silicon layers with low and intermediate resistivity were investigated with a contact-free capacitance versus voltage method. The low resistivity sample with 0.15 Ohm cm had long-term repeatability and reproducibility over 3 days with a fractional standard deviation of 0.8%. The intermediate resistivity epi layer with 6.2 Ohm cm had a long term repeatability with a fractional standard deviation of 0.16%. The fully automated CV tool measures with an electrode 0.5 μm above the wafer surface. A particle detection system ensures that there are no defects at the measurement site. This non-contact method has clear advantages over conventional methods such as mercury-CV or four-point-probe for determining doping concentration and doping depth profiles.